1. Field of the Invention
The present invention relates to a driving device used for a copying machine or a printer, and an image forming apparatus equipped with the driving device.
2. Description of the Related Art
Conventionally, in order to solve problems with consumption or deterioration of developer in an inline type color image forming apparatus using, for example, the electrophotographic process, a method for separately controlling rotations of an electrophotographic photosensitive member (photosensitive member) and a development device to minimize rotation of the development device is considered.
Further, in order to achieve low cost and reduction in size, a method for driving the photosensitive member and the development device using one motor, and providing a clutch that controls a state of rotation or stop of a driving system of the development device is devised.
An electromagnetic clutch or a spring clutch is often used in the driving system of the development device of the conventional image forming apparatus. However, this configuration has problems of a relatively high cost, a limited shape, and possible occurrence of operation failure caused by slip.
On the other hand, Japanese Patent Application Laid-Open No. 2003-208024 (Patent Document 1) discusses a mechanical clutch provided on a driving system of a development device. The mechanical clutch, by rotation of a lever member provided with a cam surface, causes a releasing member provided with a cam surface that engages with the cam surface of the lever member, and a driving side engaging component moved by the releasing member, to axially move. Accordingly, the mechanical clutch performs coupling and releasing of a drive between the driving side engaging component and an idler side engaging component. The driving side engaging components urged by a coil spring in a direction in which the driving side engaging component meshes with the idler side engaging component. The releasing member, when moved axially by the lever member, moves the driving side engaging component in a direction in which it releases the driving side engaging component from the idler side engaging component against a force of the coil spring.
In order to further reduce consumption and deterioration of the developer, a quick switching between coupling and releasing is required for the above-described mechanical clutch. Therefore, it is required to make a slope of the above-described cam surface as steep as possible.
However, the above-described mechanical clutch has the following issues to be improved.
That is, in the above-described mechanical clutch, a state where apexes of respective cams of the releasing member and the lever member are in contact with each other is a state where coupling of a drive is released. Then, when changing the state to a coupling state of the drive by rotating the lever member from this state, the releasing member moves axially along the cam surface by an urging force of the coil spring. Therefore, in a case where the cam surface has a steep angle, for example, for a quick coupling, there is a possibility that a collision between the releasing member and the lever member occurs. Accordingly, rotation of the photosensitive member which is the most important in terms of an image formation becomes unstable. As a result, d streaks may be produced on images at a timing of collision of the cams.
Therefore, the mechanical clutch as described above may be unsuitable in some cases for the configuration for simultaneously driving the photosensitive member and the development device using one motor. As a result, conventionally, in the configuration for driving the photosensitive member and the development device using one motor, there is not a mechanical clutch superior in cost or image stability, which enables on-and-off of the drive to the development device without affecting stability of rotation of the photosensitive member even in the middle of rotating the photosensitive member.